This Is a Giant Shipworm. You May Wish It Had Stayed In Its Tube.

Photo

A giant shipworm removed from its tube.Credit
Marvin Altamia

At the top, two flesh-toned siphons swish water over massive gills. At the bottom, a slimy, eyeless head resembles a mix of wet lips and diseased tonsils. In between, a glistening gunpowder blue body stretches up to four feet long. Instead of eating, bacteria in the creatureâs gills helps it suck energy from sulfur. The whole thing is sheathed in a tusklike tube created from its secretions of calcium carbonate.

Behold, the giant shipworm, your newest living nightmare.

In a study published Monday in Proceedings of the National Academy of Science, Daniel Distel, a microbiologist at Northeastern University, and colleagues described a live one for first time. Its symbiotic relationship with bacteria provides clues to how the giant shipworm evolved its strange way of eating, and may enrich our understanding of infection in humans.

âWe were used to shipworms, which are very delicate creatures and much smaller,â said Dr. Distel, who spent two decades searching for a living specimen of this elongated clam. âThis thing is a really beefy animal.â

Photo

Giant shipworms live in a tusklike tube made of calcium carbonate.Credit
Marvin Altamia

Dr. Distel tracked down living animals after a student spotted people sucking them down like spaghetti on YouTube. Local researchers and fishermen helped locate the creatures at the bottom of a remote lagoon in the Philippines, where they are a delicacy called tamilok purported to have medicinal properties.

Examining the shipworms wasnât easy. Dr. Distel carefully cracked open its shell like a soft boiled egg, then slid the shipworm out and improvised a dissection.

A giant shipworm examination in a lab.

Marvin Altamia

The shipwormâs small digestive system and gills were speckled with yellow, presumably from sulfur, suggesting that it lived off hydrogen sulfide, a toxic chemical, rather than the wood pulp diet of other shipworms.

By analyzing the genomes of the shipworm along with its bacteria, as well as the enzymes it contained, Dr. Distel concluded that shipworms first ate wood, but acquired bacteria over millions of years of evolution that allowed it to mix an energy cocktail from chemicals in the seawater, mainly hydrogen sulfide from decaying wood, instead of eating the wood directly. A similar symbiotic relationship exists in a giant deep-sea mussel that is thought to have grown so big off energy from chemicals instead of organic matter.